Although it is advisable to use insulated wire for making the electrical connections, bare wires may be used if care is taken in arranging them, so that they will not touch each other or other metallic objects which would complete the circuit.

It will be found convenient if the elements of the battery are arranged upon a frame of some sort, by means of which they may be raised or lowered all together, and supported at any desired height.

* * * * *

THE ACTION OF THE SILENT DISCHARGE ON CHLORINE.

Arguing from the fact that oxygen gas, when subjected to the silent discharge, partially undergoes condensation into ozone, it seemed possible, says Mr. H.M.  Vernon, in the Chemical News, that other elementary gases, as chlorine and bromine vapor, might undergo an analogous change when subjected to the same treatment.  A glass tube, with a U-shaped index of fine bore glass tubing, was filled with purified and dried chlorine.  After passing a current of the gas through the tube for some time, the end was sealed in the blowpipe flame.  The tube was then warmed slightly, and a few bubbles of gas thus driven out.  The end of the index tube dipped under strong sulphuric acid saturated with chlorine gas, so that, on cooling, a short column of the acid was drawn up.  This served as an index for any changes of volume which might take place in the chlorine in the tube.  A silent discharge of electricity was then passed.  The volume of the gas was observed to increase slightly, but afterward it remained quite constant, even after the discharge had been passed for several hours.  We may therefore conclude that no allotropic change takes place when chlorine gas is subjected to the silent discharge of electricity, the initial increase of volume being merely due to the heating effect the discharge has upon the gas.  Into another similar tube, filled with chlorine, was introduced a small quantity of liquid bromine.

The tube thus contained chlorine saturated with bromine vapor.  The silent discharge on being passed through this tube did not produce any different effect than for chlorine alone.  So we may conclude that bromine vapor also does not undergo any allotropic condensation when subjected to the influence of a silent discharge of electricity.  The fact that oxygen gas is capable of undergoing condensation while chlorine and bromine are not is easily explained.  The oxygen atom, being divalent, is capable of uniting itself to two other atoms of oxygen or other elements, and thus with oxygen forming ozone.  The atoms of chlorine and bromine, however, being only monovalent, have all their affinity satisfied when they are united to a single other atom of chlorine and bromine.  It is not possible, therefore, that condensation can take place if the atoms remain monovalent.  Hydrogen gas and iodine vapor are in a similar manner debarred from undergoing condensation.  Mr. Vernon, therefore, comes to the conclusion that it is most improbable that any other element but oxygen will be found capable of undergoing molecular condensation when in the gaseous state and subjected to the silent discharge.